1. Technical Field
The present disclosure relates to a liquid crystal display (LCD), and more particularly, to an LCD using a light emitting diode (LED) as a light source.
2. Discussion of the Related Art
Flat panel displays, such as an LCD, a plasma display panel (PDP), and an organic light emitting diode (OLED), have been developed and have replaced a conventional display such as a cathode ray tube (CRT).
An LCD comprises a liquid crystal display panel having a TFT substrate, a color filter substrate, and liquid crystal disposed between the TFT substrate and the color filter substrate. Since the liquid crystal display panel cannot emit light by itself, the LCD may comprise a backlight unit disposed in rear of the TFT substrate. The transmittance of the light from the backlight unit is adjusted according to an alignment of liquid crystal. The liquid crystal display panel and the backlight unit are disposed in a chassis.
The backlight unit may be classified as an edge type and a direct type based on a location of a light source. The edge type backlight unit has the light source at the side of a light guiding plate and is used for a small-sized LCD such as a laptop or a desktop computer monitor. The edge type backlight unit is suitable for a thin LCD since the edge type backlight unit has a high light uniformity and endurance.
The direct type backlight unit can be used for larger LCDs and provides the entire surface of the LCD with light by disposing a plurality of light sources behind the liquid crystal display panel. The direct type backlight unit has a high brightness by using a plurality of light sources as compared with the edge type backlight unit. However, the brightness of the direct type backlight unit is not uniform.
An LED is used for a light source of a backlight unit since the LED has a high brightness and color reproducibility. The LED generates more heat than other light sources such as a Cold Cathode Fluorescent Lamp (CCFL) and an External Electrode Fluorescent Lamp (EEFL). The heat from the LED decreases the brightness of backlight and causes a color shift.
A radiating fin, a heat pipe and a cooling fan used to remove the heat from the LED cause the LCD to be heavier and thicker.